or Connect
AVS › AVS Forum › Audio › Audio theory, Setup and Chat › Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs
New Posts  All Forums:Forum Nav:

Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 219

post #6541 of 9570
Quote:
Originally Posted by jkasanic View Post

Nyal, I'm using MKSound S150 Series II's for my LCR.  When I look at the literature for these speakers found here, I read things like:




And:




My question is what does this imply about the characteristics of my speakers as they apply to room treatments?  What is the best means to confirm the off-axis response?  Is it through FR sweeps along the width of the room?  I'd appreciate some more insight into understanding how the two (speaker's response and walls) interact and what conclusions to draw from this interaction.

Thanks for your contributions, btw!

Joe

You can measure the speaker's off axis using your REW. Bring the speaker out to the middle of the room, put a bunch of cushions / comforters on the floor and the mic 18" away from the speakers. Keep the mic in the same place and turn the speakers. You should end up with something like this:

\

The above is a nicely behaved speaker. This speaker is ok, but notice the issues around 1-3kHz, which are crossover related issues. Also note that this speaker has a lot more SPL off axis than the one above.

Gear mentioned in this thread:

post #6542 of 9570
ok, here is what happened after I moved the subs sideways and into the 1/4 and 3/4 point. I also moved the speakers out wider and toed in firing directly at the MLP.

first is the new raw and after all EQ graphs

Raw



post EQ



raw waterfall


post EQ waterfall


raw Spectrogram


post EQ spectrogram




here is my previous position with subs and speakers.

raw response first





And here was post EQ





in closing it doesn't really seem much different to me as far as looks of graphs. I have an uneducated hunch my 100-200 hz is vertical issues. Perhaps a couple of panels over the MLP. But 4 inches is not enough though right? Hmmm...I can't say for sure if Audyssey is increasing decay times because I also have a low shelf filter, and PGM 2 on my subversives on. An important note is that we like the subs physically where they are at now better than the corners. It frees up corner room and allowed the speakers to sit wider which improved the size of the sweet spot bubble.
Edited by jlpowell84 - 11/8/13 at 11:56pm
post #6543 of 9570
Quote:
Originally Posted by jlpowell84 View Post

first is the new raw...


here is my previous position


in closing it doesn't really seem much different to me as far as looks of graphs.
Looks like it lifted the dip between 50-60 Hz, from a deep 12dB to a shallower 5dB.
Quote:
Originally Posted by jlpowell84 View Post

It frees up corner room and allowed the speakers to sit wider which improved the size of the sweet spot bubble.
Now that the corners are freed up, consider floor to ceiling (or floor to soffit) bass traps there.
post #6544 of 9570
Quote:
Originally Posted by J_P_A View Post

Quote:
Originally Posted by mtbdudex View Post

.....
There is something going on with the Mac REW., I just got a brand new MacBook Pro Retina, so will "play" with REW on that in near future and feedback here.
....

Keep me updated on what you find. I put together the guide you linked to. I also had trouble with my Mac reverting back to the internal mic, but after setting it to built-in device it seemed to work properly. Granted, I haven't had a lot of time to play with it since then.

Hi JPA, so you are "EmagSamurai" at HTS?
I'm trying a little twist....as I have my "old" but calibrated EMC8000, so I'm attempting to go thru the Moble-pre USB for that into my Mac Book Pro Retina (new, 1 week old), then out thru HDMI into my Denon-4520.

I'm getting frustated.....I can get the Mac side to see the EMC8000 fine on input - tap/tap the mic face to confirm, and the output thru HDMI to select speakers.....but in REW it keeps going to internal mic not USB mic, in REW when I tap/tap the EMC8000 it reads nothing, but tap/tap the internal mic it reads that....

Somehow REW is not reading the Input correctly.....

Done the LineIn app to map, had AudioMidi setup, still not mapping input correctly in REW.
>>I keep REW to default, as the mapping is done outside of that
I've burned 1.5 hours and am about to go back to analog........just HDMI seems so easy to switch speaker-to-speaker (and I have 2 EMC8000's already, my 1st one from 2008 is not calibrated, so buying a USB mic is outta the equation for now)

I'll feedback @ HTS the details, as JohnM there might be interested in it.

sorry for rant, now 2 hrs and tired of these tech side issues mad.gif
post #6545 of 9570
^
You have to quit REW, make changes in Audio MIDI Setup then start REW again.
post #6546 of 9570

My experience--tuned membrane traps.

 

Background:  My room is already heavily treated for bass resonances, but there are still resonances around the 40Hz range that have been difficult to control.  I have been interested in tuned membrane traps because they are designed to tame a very specific and narrow frequency band.  Having done a lot of business with GIK, I researched their Scopus product, which is a tuned membrane trap coming in three standard models, the T-40, T-70, and T-100, targeted for 40Hz, 70Hz, and 100Hz, respectively.  Each is a 2'x2' panel, varying in thickness from 4.5" for the T-70 and T-100, and 10.25" for the T-40.  GIK will build special-order Scopus traps that target any frequency at no additional cost.

 

I have limited space left in my listening room, and felt that I could accommodate no more then four panels.  I ordered them, and they arrived earlier this week:

 

 

The traps are a plywood box, sealed in back, and covered with the typical GIK fabric. The traps are heavy, 30lbs each.  Build quality is good.

 

I have received differing recommendations regarding where to place the traps to maximize effectiveness.  Some have recommended placing the traps according to which room dimension is creating the standing wave.  Others recommended generating a standing wave at the target frequency using REW's signal generator, and then measuring the SPL at various potential mounting locations. looking for the highest SPL.  I decided on the latter method.  As expected, locations at boundaries between walls, wall and floor, and wall and ceiling produced the highest SPL readings.  The highest reading, by almost 10dB, was along the front wall on the floor.  That is where I placed the traps:

 

 

I took careful measurements before and after installing the traps, being careful to place the mic in the same spot.  results:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

So, how effective are the membrane traps?  A slight frequency response at 48Hz is several dB's better.  It's hard to say, but the Waterfalls may show a slight improvement below 40Hz.  The Spectrogram, our new favorite measurement, shows a decrease in ringing at 40Hz, from 620ms to 490ms, which isn't bad.

 

So, given the expense of the four Scopus traps, did I get my money's worth?  Not sure.  Feedback would be appreciated.


Edited by AustinJerry - 11/9/13 at 9:51am
post #6547 of 9570
^
Response looks worse with the traps installed. Don't they need to be mounted to the wall? Might make a difference. I'd ask GIK.

By the way, can't read the labels in your graphs. They are way too small.
Selecting the same colors in the waterfalls makes it easier to compare.
post #6548 of 9570
Quote:
Originally Posted by markus767 View Post

^
Response looks worse with the traps installed. Don't they need to be mounted to the wall? Might make a difference. I'd ask GIK.

By the way, can't read the labels in your graphs. They are way too small.
Selecting the same colors in the waterfalls makes it easier to compare.

 

They are on the wall, or at least against the wall.

post #6549 of 9570
^
But not fixed to the wall...
post #6550 of 9570
here is audyssey vs no audyssey XT32....MUCH flatter and doesnt mess with the response...+/-3 down to 10hz...both unsmoothed



smoothed:


here is R + L + SW 1/6 full range and waterfall:




thoughts??
post #6551 of 9570
Quote:
Originally Posted by markus767 View Post

^
But not fixed to the wall...

 

Kindly explain the scientific logic behind improved sound of traps placed against a wall vs. traps mounted against the wall.  Does it have something to do with the rigidity of the coupling between the trap and the wall?  Do you have supporting evidence?

post #6552 of 9570

@ Brian,

 

Why measure only the sub+left unsmoothed?  Do you have sub+left+right un-smoothed?

 

And why 800ms on the waterfall?  Our target is to use 450ms.  Most waterfalls look great with a 800ms window.  And are you going to generate the Spectrogram?

 

I agree that the post-Audyssey response on the Sub+Left looks considerably better.

post #6553 of 9570
Quote:
Originally Posted by AustinJerry View Post

Kindly explain the scientific logic behind improved sound of traps placed against a wall vs. traps mounted against the wall.  Does it have something to do with the rigidity of the coupling between the trap and the wall?  Do you have supporting evidence?

I'm pretty sure the scopus are sealed box panel traps so it should not matter?

I have to agree, measurements look generally worse with Scopus, especially in 60Hz region. What tuning frequency are the traps?

The thing is with any pressure based trap (like the Scopus) they need to go in areas of high pressure to be effective. Easy way to find these is to play sine wave at the target frequency and either walk around room and listen for where it is loudest or use SPL meter or mic.
post #6554 of 9570
Quote:
Originally Posted by AustinJerry View Post
 

 

So, given the expense of the four Scopus traps, did I get my money's worth?  Not sure.  Feedback would be appreciated.

 

Hmmm. IDK what to think, Jerry. You seem to have made some gains on the swings and lost some on the roundabouts. (Roundabouts are carousels - IDK if you have that saying in the US).

 

I was hoping for more TBH after an investment of over $1,000. Can you detect any improvement when listening?

 

As you know, I was hoping membrane traps would help me at 45-55Hz but now I am not so sure - I think I would want bigger gains to be happy with the expenditure.

 

BTW, I can read the labels on your graphs with no problem here.

post #6555 of 9570
Quote:
Originally Posted by AustinJerry View Post

@ Brian,

Why measure only the sub+left unsmoothed?  Do you have sub+left+right un-smoothed?

And why 800ms on the waterfall?  Our target is to use 450ms.  Most waterfalls look great with a 800ms window.  And are you going to generate the Spectrogram?

I agree that the post-Audyssey response on the Sub+Left looks considerably better.

Ok ill repost. I set it to 800 by accident. It actually looks good in 450 other than <30hz. But my room is untreated.

I also thought you shouldn't post r l sw except for waterfall (according to the guide)
post #6556 of 9570
Quote:
Originally Posted by Nyal Mellor View Post

I'm pretty sure the scopus are sealed box panel traps so it should not matter?

I have to agree, measurements look generally worse with Scopus, especially in 60Hz region. What tuning frequency are the traps?

The thing is with any pressure based trap (like the Scopus) they need to go in areas of high pressure to be effective. Easy way to find these is to play sine wave at the target frequency and either walk around room and listen for where it is loudest or use SPL meter or mic.

Scopus are indeed sealed boxes. The ones I installed are tuned for 40Hz, so they shouldn't be having an effect at 60Hz. I attribute the differences at 60Hz to be measurement anomalies, even though I tried to place the mic in the same spot.

And if you re-read my post, I did place the traps at the spot that yielded the highest SPL at the 40Hz target frequency.
post #6557 of 9570
Quote:
Originally Posted by sdurani View Post

Looks like it lifted the dip between 50-60 Hz, from a deep 12dB to a shallower 5dB.
Now that the corners are freed up, consider floor to ceiling (or floor to soffit) bass traps there.

Yes you are right smile.gif
I certainly appreciate the help! I plan of 15x15 soffits from floor to ceiling corners (minus a 3ft gap for wall air conditioner frown.gif ) and also the same soffits all along the ceiling to wall junctions mounted. Stuffed with pink fluffy. Or rather a 15x9.25 and a 15x6.5 tacked/stapled to the top of the soffit and hanging down. Don't want to stuff it actually because then I would change the absorption characteristics for the worse.
post #6558 of 9570
Man Jerry, Im sorry the improvements were not more drastic, or at least not moving backwards. It may mean nothing coming from me but I feel for ya smile.gif
I personally would be quite disappointed if that was my expense and results. Perhaps show Brian at GIK? Sorry if I overstepped my boundaries, mean no ill intent smile.gif
post #6559 of 9570
Quote:
Originally Posted by Brian Fineberg View Post

Ok ill repost. I set it to 800 by accident. It actually looks good in 450 other than <30hz. But my room is untreated.

I also thought you shouldn't post r l sw except for waterfall (according to the guide)

Sorry, Brian, I don't mean to give you a mixed message. I don't recall this recommendation being in the guide. In general, I think if you publish left + sub! you should post right + sub as well in order to get the full picture. And I don't think there is anything wrong with posting l+r+ sub if it is the bass frequencies that you are trying to show. It's all good.
post #6560 of 9570
Gotcha. I will post when i get home!! Thanks for the help!!
post #6561 of 9570
Quote:
Originally Posted by AustinJerry View Post

Scopus are indeed sealed boxes. The ones I installed are tuned for 40Hz, so they shouldn't be having an effect at 60Hz. I attribute the differences at 60Hz to be measurement anomalies, even though I tried to place the mic in the same spot.

And if you re-read my post, I did place the traps at the spot that yielded the highest SPL at the 40Hz target frequency.

To be sure, I would test again, without moving the mic, with the traps and then without them.
post #6562 of 9570
Quote:
Originally Posted by AustinJerry View Post

Scopus are indeed sealed boxes. The ones I installed are tuned for 40Hz, so they shouldn't be having an effect at 60Hz.
They do though. The bandwidth is wider than a single frequency. GIK only posts a tiny graphics for the boxes:

scopus_graph_sm.jpg

If you squint, you see that at 60 Hz, the coefficient of absorption is ~0.4 vs about 1.05 at its tune frequency of 40 Hz. In other words you are getting about 40% absorption at 60 Hz. They are just like a notch filter in a parametric EQ that would also have certain bandwidth.

That is not the full story though. The measurements at very low frequencies could be subject to fair bit of error (the lab's low frequency response is not uniform in all directions). For the 40 Hz trap, they only have three data points (30, 40 and 63) so even my analysis above is dicey. And manufactured products, environmental conditions and such may all change these numbers.

Tuned traps are very difficult to deploy for these reasons.
post #6563 of 9570
Quote:
Originally Posted by kbarnes701 View Post

I was hoping for more TBH after an investment of over $1,000.
If Jerry's investment had been described using a different number, noting that the membrane traps covered only 1.5% of the surface area of his room, would you still have been hoping for more or would that percentage have made your expectations more realistic?

Speaking of investment, saw this a few months ago:
Quote:
Originally Posted by Ethan Winer View Post

I have 55 bass traps, diffusers, and other panels, that were installed over several years.
Even if only half of those are bass traps, that's still hundreds of square feet of coverage.
post #6564 of 9570
Quote:
Originally Posted by sdurani View Post

If Jerry's investment had been described using a different number, noting that the membrane traps covered only 1.5% of the surface area of his room, would you still have been hoping for more or would that percentage have made your expectations more realistic?

Speaking of investment, saw this a few months ago:
Even if only half of those are bass traps, that's still hundreds of square feet of coverage.

The square ft issue and % coverage is an interesting angle. But surely if you have to buy 20 of these traps to be effective, the cost ratio certainly is not.

But on this issue, id say 90% of my walls have either absorbers, diffusers or reflectors in front of them (the diffusers and reflectors have absorbent behind them as well). 30% of my ceiling and 20% of my floor.
Edited by jim19611961 - 11/9/13 at 1:31pm
post #6565 of 9570
Quote:
Originally Posted by jim19611961 View Post

The square ft issue and % coverage is an interesting angle.
Only because mid-40Hz waves are radiating spherically and hitting every single surface of the room.
Quote:
Originally Posted by jim19611961 View Post

But surely if you have to buy 20 of these traps to be effective, the cost ratio certainly is not.
Sure, unless you're the manufacturer, and even then...

I was just trying to put things in perspective, using a metric that was more proportional to difference Jerry measured.
post #6566 of 9570
Quote:
Originally Posted by sdurani View Post

Only because mid-40Hz waves are radiating spherically and hitting every single surface of the room.

Isnt that true of all frequencies at or below the 4 pi spherical radiation threshold of the speaker?
post #6567 of 9570
Quote:
Originally Posted by jim19611961 View Post

Isnt that true of all frequencies at or below the 4 pi spherical radiation threshold of the speaker?
Sure, I just used that number because that was the frequency Jerry was targeting.
post #6568 of 9570
So, forgetting for a moment the cost, is anyone seeing a worthwhile improvement, or should I, like Jim recommends, re-measure without moving the mic?

Remember, I can still return the product, although I would incur a $240 shipping expense.
post #6569 of 9570
Quote:
Originally Posted by sdurani View Post
 
Quote:
Originally Posted by kbarnes701 View Post

I was hoping for more TBH after an investment of over $1,000.
If Jerry's investment had been described using a different number, noting that the membrane traps covered only 1.5% of the surface area of his room, would you still have been hoping for more or would that percentage have made your expectations more realistic?

Speaking of investment, saw this a few months ago:
Quote:
Originally Posted by Ethan Winer View Post

I have 55 bass traps, diffusers, and other panels, that were installed over several years.
Even if only half of those are bass traps, that's still hundreds of square feet of coverage.

 

Very good point. When you put it like that... 

 

I think it means I won't bother with them. I only have physical room for 4 at the most and for the difference they appear to make I don't think they are worth the price. I know we are chasing ever more diminishing returns, but for $1,000 I'd be wanting more than they appear to be able to do. Even if I had space for more, at what price would any improvement come? 2 grand, 3 grand??

post #6570 of 9570
Quote:
Originally Posted by jim19611961 View Post
 
Quote:
Originally Posted by sdurani View Post

If Jerry's investment had been described using a different number, noting that the membrane traps covered only 1.5% of the surface area of his room, would you still have been hoping for more or would that percentage have made your expectations more realistic?

Speaking of investment, saw this a few months ago:
Even if only half of those are bass traps, that's still hundreds of square feet of coverage.

The square ft issue and % coverage is an interesting angle. But surely if you have to buy 20 of these traps to be effective, the cost ratio certainly is not.

 

That's my thinking too. 20 would have cost Jerry a staggering $5,000. Even if he had room for them.

 

 

Quote:

 But on this issue, id say 90% of my walls have either absorbers, diffusers or reflectors in front of them (the diffusers and reflectors have absorbent behind them as well). 30% of my ceiling and 20% of my floor.

 

I may look at mine in this light. I have more potential areas I could treat... especially now I am making my own panels and they cost very little.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Audio theory, Setup and Chat

Gear mentioned in this thread:

AVS › AVS Forum › Audio › Audio theory, Setup and Chat › Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs